Field of the Present Invention
The present invention relates generally to electromagnetic field-based bio-sensing and bio-imaging, and in particular, to a handheld probe-based electromagnetic field technology that allows clinicians to assess functional and pathological conditions of biological tissue on-line at the point of care
Background
The successful management of a fractured bone involves an understanding of the two major components of any limb segment. These two components are the osseous or boney element and the soft tissue elements. Soft tissue elements are the skin, muscle, nerve and vessels while osseous element includes only the bone. The diagnosis and evaluation of the boney component is obvious to the treating physician by radiographic studies. The accurate assessment of the soft tissue component of the injured limb segment remains a major deficiency in management of fractures. To date several methods; such as laser Doppler and transcutaneous oxygen tensions have been attempted but they have been no better than clinical judgment. None of these methods have correlated with outcome. Consequently there is an important need to develop a simple effective method of assessing soft tissue viability.
It is important to understand soft tissue injury, as this component is often the determinant of the final outcome. The soft tissues provide the blood supply for the bone to heal, provide the coverage for the bone and the muscles, nerves and vessels provide for a functional outcome following injury. With the advent of higher energy trauma, more and more significant soft tissue disruption is being seen. The clinical problem exists with closed or open fractures as there is no method at the present to objectively evaluate soft tissue damage prior to surgical treatment. The surgical approach causes further damage to the soft tissues leading to necrosis, wound slough and infection. Consequently, surgeons require a method to accurately and objectively establish soft tissue viability so as to minimize the complication rate. In addition, associated injuries to the muscle such as a compartment syndrome and arterial disruption require soft tissue viability assessment to plan an appropriate management. A compartment syndrome occurs after an injury to an extremity when the obligatory muscle swelling becomes excessive. If the involved muscle is contained in an enclosed fascial space, this swelling will compromise arteriolar muscle blood flow leading to what has been called “a heart attack” of skeletal muscle. The issue of early diagnosis of compartment syndrome is very important, and is not limited to the management of fractures. The swollen limb without fracture is commonly seen and should be urgently assessed by orthopedic specialists. Undiagnosed compartment syndrome leads to muscle necrosis, contracture and irreversible neurological deficits. Extensive irreversible muscle damage can eventually result in sepsis or amputation. The incidence of complications is related to the speed in diagnosis and timing of fasciotomy. For this reason, delay of diagnosis and lack of aggressive surgical intervention has resulted in a high rate and amount of indemnity payment. In most patients, clinical examination is the most sensitive method of early diagnosis but in obtunded, head injured, or critically ill patients physical signs and symptoms are unreliable. Objective data is required in these situations and these measurements must be accurate and reproducible for diagnosis. Currently pressure measurements are the best means of determining need for fasciotomy but clinicians are unable to reach a consensus as to the critical pressure threshold. In addition, these tests are invasive, technique dependent, subjective and position sensitive.
Clinicians are always looking for simple non-invasive painless tests which provide the accurate clinical data necessary to make a rapid diagnosis. As to the monitoring of soft tissue viability in assessment of crush injuries, free muscle flap viability, arterial injury and reperfusion, at present there is not a consistent reliable instrument that is safe and non invasive. In this aspect, the concept of current invention is very appealing to the orthopaedic trauma surgeons as a method of non-invasive tissue viability assessment and monitoring. This technique would provide the surgeon with a measure of the soft tissue viability associated with a fracture. This would allow the treating surgeon to time surgical intervention appropriately, to avoid major disastrous complications and to be able to prognosticate the long-term functional outcome for patients. The invented technology combined with plain radiology in the acute emergency situation would provide the treating surgeon with a complete assessment of both components of any given injury. This would enhance drastically the ability of surgeons to provide quality and effective care for extremity injuries.
Various technologies making use of electromagnetic field phenomena in diagnosing, imaging, and treating various medical conditions. One of these technologies, electromagnetic tomography (EMT), is a relatively recent imaging modality with great potential for biomedical applications, including a non-invasive assessment of functional and pathological conditions of biological tissues. Using EMT, biological tissues are differentiated and, consequentially, can be imaged based on the differences in tissue dielectric properties. The dependence of tissue dielectric properties from its various functional and pathological conditions, such as blood and oxygen contents, ischemia and infarction malignancies has been demonstrated. Two-dimensional (2D), three-dimensional (3D) and even “four-dimensional” (4D) EMT systems and methods of image reconstruction have been developed over the last decade or more. Feasibility of the technology for various biomedical applications has been demonstrated, for example, for cardiac imaging and extremities imaging. Various patents and patent applications have discussed these technologies, including U.S. Pat. Nos. 5,715,819, 6,026,173, 6,332,087, 6,490,471, and 7,239,731, and U.S. patent application Ser. No. 13/173,078 (filed Jun. 30, 2011 and published on Jan. 12, 2012 as U.S. Patent Application Publication No. 2012/0010493 A1) and U.S. Patent Application Ser. No. 61/801,965 (filed Mar. 15, 2013) (a copy of the latter of which is attached hereto as Appendix A). The entirety of each of these patents and patent applications (and any publication of same) is incorporated herein by reference at least so far as such incorporation is consistent with the disclosure set forth herein.
Unfortunately, traditional EMT technologies, while producing very useful results, have required equipment that is physically cumbersome and difficult to use. This can be true both for the technician, diagnostician, or the like as well as the person or animal who is being studied. With regard to latter, the discomfort caused by the imaging chamber can also be significant. The size and weight of the equipment also makes it very difficult to use the equipment in the place where it is assembled; disassembling and moving the equipment is not very feasible. Finally, the use of arrays of antenna and other equipment creates significant complexity and cost. Thus, a need exists for technology that produces similar results but in a cheaper, more convenient, and more comfortable physical form. In particular a need exists for a more convenient, probe-based, hand-held technology that allows clinicians to assess functional and pathological conditions of biological tissue on-line at the point of care.